Cardiac surgery is conventionally performed with the patient's heart stopped and with circulation of blood maintained by extracorporeal cardiopulmonary bypass, a state known as cardioplegic arrest. Cardioplegic arrest conventionally requires the creation of a large incision in the chest, known as a sternotomy or thoracotomy, to expose the heart and great vessels of the thorax. Through this large incision, a steel clamp, called a cross-clamp, is placed around the aorta between the coronary arteries, which deliver blood to the heart muscle, and the brachiocephalic artery, which delivers blood to the head and neck. The clamp is closed so as to collapse the aorta, thereby partitioning the heart and coronary circulation from the remainder of the arterial system downstream of the cross-clamp. Pharmaceutical agents may then be delivered into the coronary arteries or aorta upstream of the cross-lamp so as to arrest cardiac function. Circulation of blood is maintained throughout the body by placing a venous drainage cannula in a major vein or in the right side of the heart to withdraw venous blood, routing the blood to an extracorporeal oxygenator, and pumping the blood back into the arterial system through a cannula positioned in a major artery, typically in the aorta just downstream of the cross-clamp.
While cardiopulmonary bypass with cardioplegic arrest is currently the gold standard for performing most cardiac surgical procedures, conventional techniques suffer from several drawbacks. Important among these are the high degree of pain and trauma, risk of complications and long recovery time which result from median sternotomy and other types of gross thoracotomy. Furthermore, the use of a cross-clamp on a calcified or otherwise diseased aorta can produce serious complications such as embolization of plaque, potentially leading to stroke and other neurological problems.
In U.S. Reissue Pat. No. Re 35,352 to Peters, which is assigned to the assignee of the present invention and is hereby incorporated herein by reference, it is suggested that the use of a cross-clamp to achieve cardioplegic arrest could be avoided through the use of an endovascular balloon occlusion catheter positioned from a femoral artery into the ascending aorta. A balloon at the distal tip of the occlusion catheter can be expanded to occlude the aorta between the coronary arteries and brachiocephalic artery, and cardioplegic fluid then delivered through a lumen in the catheter into the aorta upstream of the balloon so as to arrest the heart. Cardiopulmonary bypass is established by placing arterial and venous cannulae in a femoral artery and femoral vein, respectfully, and routing the patient's blood through an extracorporeal oxygenator and pump.
While the endovascular technique proposed in the Peters patent is useful in many cardiac surgeries to avoid the need for median sternotomy and aortic cross-clamping, the technique can have disadvantages in some situations. For example, in patients with severe peripheral vascular disease, the balloon occlusion catheter may be difficult to introduce into the femoral arteries and to advance transluminally into the ascending aorta.
Another technique for inducing cardioplegic arrest without the use an aortic cross-clamp is proposed in U.S. Pat. No. 5,312,344 to Grinfeld. This technique involves the placement of a balloon occlusion catheter into the ascending aorta directly through a puncture in the aortic wall. The balloon occlusion catheter has an occlusion balloon at its distal tip which is used to occlude the aorta between the coronaries and the brachiocephalic artery. The catheter further includes an arterial return lumen through which blood may be delivered into the aorta downstream of the balloon, eliminating the need for a separate arterial return cannula.
The Grinfeld technique, however, also suffers from a variety of disadvantages. First, because the catheter is introduced through the ascending aortic wall, the technique requires dissection and retraction of the various tissues surrounding the ascending aorta to expose the vessel. This is particularly difficult if the procedure is to be performed minimally-invasively through trocars or small incisions, without a median sternotomy or other gross thoracotomy. In addition, many patients who receive cardiac surgery have some degree of aortic calcification or other aortic disease. In such patients, it is undesirable to puncture the aortic wall with a catheter as taught by Grinfeld, as this could embolize plaque, initiate or aggravate an aortic dissection, or create other problems. Finally, in Grinfeld's technique, because oxygenated blood is returned to the arterial system through a lumen within the aortic occlusion catheter itself, should the surgeon desire to remove the occlusion balloon from the aorta due to a balloon puncture or other problem, the patient must first be re-warmed and weaned from extracorporeal cardiopulmonary bypass before the balloon can be removed, lengthening the procedure considerably.
What is needed therefore, are devices and methods for inducing cardioplegic arrest and maintaining circulation of oxygenated blood which do not require median sternotomy or other gross thoracotomy and which eliminate the need for aortic cross-clamping, but which overcome the disadvantages of known endovascular balloon occlusion devices. The devices and methods should be useful in patients having severe peripheral vascular disease as well as in those having-aortic calcification, without creating a high risk of embolization, aortic dissection, or other complications. The devices and methods should further avoid the need to directly access the aorta and the associated need to dissect and retract the surrounding tissues. Moreover, the devices and methods should optionally allow occlusion of the aorta to be discontinued and any occlusion device to be removed from and replaced in the aorta without weaning the patient from cardiopulmonary bypass.